ROME (REUTERS).- A team of marine archaeologists using sonar scanners have discovered four ancient shipwrecks off the tiny Italian island of Zannone, with intact cargoes of wine and oil.

The remains of the trading vessels, dating from the first century BC to the 5th-7th century AD, are up to 165 meters underwater, a depth that preserved them from being disturbed by fishermen over the centuries.

"The deeper you go, the more likely you are to find complete wrecks," said Annalisa Zarattini, an official from the archaeological services section of the Italian culture ministry.

The timber structures of the vessels have been eaten away by tiny marine organisms, leaving their outlines and the cargoes still lying in the position they were stowed on board.

"The ships sank, they came to rest at the bottom of the sea, the wood disappeared and you find the whole ship, with the entire cargo. Nothing has been taken away," she said.

The discoveries were made through cooperation between Italian authorities and the Aurora Trust, a U.S. foundation that promotes exploration of the Mediterranean seabed.

The vessels, up to 18 meters long, had been carrying amphorae, or large jars, containing wine from Italy, and cargo from North Africa and Spain including olive oil, fruit and garum, a pungent fish sauce that was a favorite ingredient in Roman cooking.

Another ship, as yet undated, appeared to have been carrying building bricks. It is unclear how the vessels sank and no human remains have been found.

Trade RoutesThe vessels are the second "fleet" of ships to be discovered in recent years near the Pontine islands, an archipelago off Italy's west coast believed to have been a key junction for ships bringing supplies to the vast warehouses of Rome.

"One aim was to test the hypothesis that the Pontine islands, which are very small and which were barely inhabited in antiquity, were really important maritime staging posts because they had very good natural harbors," Zarattini said.

The team hope to find a secondary cargo of smaller items which they believe would have been stowed in straw and may be well preserved under the crustacean-clad sediments.

Last year, the project found five wrecks off nearby Ventotene, an island used in Roman times to exile disgraced Roman noblewomen. The Emperor Augustus sent his daughter Julia there to punish her for adultery.

Italy has signed a new UNESCO agreement that requires them to leave the wreckage in place, potentially opening the way to would-be treasure hunters although Zarattini said the benefits in terms of tourism outweighed the risks.

"We think the sea, which is particularly beautiful around these islands, can become a real museum," she said.

"In the future, not so far off, a lot of people will be able to go down and see the wreckage themselves."